Flexible actuator

ABSTRACT

A flexible actuator is disclosed which comprises an expansion chamber defined by an inner wall of an expandable girdle, the expandable girdle being connected to at least two anchoring points. The expansion chamber has at least one fluid inlet to allow pressurized fluid into the chamber. The expansion chamber capable of acquiring a minimum volume and a maximum volume. The flexible actuator is adapted to transform a fluid pressure force against the inner wall of the expandable girdle into a traction force at the two anchoring points when the expansion chamber is inflated by the pressurized fluid entering through the fluid inlet.

FIELD OF THE INVENTION

[0001] The invention relates to a mechanical actuator and more specifically, to a flexible hydraulic or pneumatic actuator adapted to generate forces capable of imparting movement or motion to objects.

BACKGROUND OF THE INVENTION

[0002] There exist in the industry a wide variety of actuators adapted to impart forces and motion to various articulated structures or objects to perform certain tasks such as hydraulic or pneumatic piston-cylinders assemblies. Hydraulic piston-cylinders assembly are common and have been used extensively where high forces need to be generated such as to move heavy objects. Examples of use of hydraulic piston-cylinders assembly are in tractors, back hoes, bulldozers and heavy machinery in general. Hydraulic piston-cylinders assemblies are also used for smaller equipment where high forces are required such as in various industrial equipment and various machinery. The list of use hydraulic piston-cylinders assembly is almost endless.

[0003] A piston-cylinder assembly consists of a hollow cylinder and a piston head connected to a piston rod, both housed into the cylinder. The piston rod exits the cylinder at one end and is connected to an object to be moved of a force is to be applied to perform Work. There are two fluid inlet-outlets at each end of the cylinder. Pressurized fluid is introduced into the cylinder and the application of the fluid pressure on the piston head's surface generates a force on the piston equal to the pressure multiplied by the effective area of the piston head. The piston rod connected to the piston head is forced to move through the opening of the cylinder by the fluid's debit and in turn imparts a movement or a force to the object it is connected to.

[0004] Hydraulic piston-cylinders assemblies are made of steel to withstand the high pressure and high forces generated. Furthermore, since they are designed to generate a superior compression force, their entire assembly must be rigid in order to apply a compression force otherwise the piston-cylinder assembly will buckle. They are therefore heavy and bulky. Piston-cylinders assemblies'are also capable of generating traction forces opposite the compression force by simply reversing the fluid's debit such that fluid pressure is applied to the back of the piston head thereby retracting the piston rod. The traction force generated is less than the compression force generated since the effective piston head area is diminished by the piston rod being connected to the back of the piston head.

[0005] Piston-cylinders assemblies'work linearly; their basic design limiting their actions to a rectilinear movement forward or backward. The inherent rigidity of the steel parts further limits the motion they may provide to the longitudinal axis of the piston rod. The rigidity of the cylinder and of the piston rod prevents them from deviating from the linear axis and restricts their action to that specific axis. Furthermore, the piston rod movement must be free of any obstacle. Since its movement is restricted to a linear motion, the piston-cylinder assembly cannot touch other components through its entire range of motion, otherwise the motion of the piston rod will be blocked or the component in the piston rod's path will be moved or broken.

[0006] These limitations present a problem when complex movements are required and space is limited. Combining two or more piston-cylinder assemblies'on a single structure in order to perform complex movements is difficult because of their rigidity and the limitation of their movement to a simple line. Also the shear size and weight of piston-cylinder assemblies'makes for a very bulky and heavy system.

[0007] Pneumatic piston-cylinder assemblies are also common in the market place; these are made of lighter materials but generate smaller forces than their hydraulic counterpart. However the same limitation of linear motion applies for these and they are also difficult to combine together to generate complex movements.

[0008] Other actuators exists such as endless screws or even electric motors which are able to generate various forces and movements but these are also restricted to either rotational or linear movements and they are almost impossible to combine together to generate complex movements due to their rigidity and lack of flexibility.

[0009] Thus there is a need to provide a light flexible actuator adapted to generate a substantial forces and which can be combined to other flexible actuators to generate complex movement.

OBJECTS AND STATEMENT OF THE INVENTION

[0010] It is an object of the invention to provide a flexible actuator capable of imparting a force to an object or an articulated structure.

[0011] It is a further object of the invention to provide a flexible actuator which can follow various displacement trajectories.

[0012] It is a further object of the invention to provide a flexible actuator that can be combined to other actuators to perform Work.

[0013] As embodied and broadly described herein, the invention provides a flexible actuator comprising:

[0014] an expansion chamber defined by an inner wall of an expandable girdle, the expandable girdle connected to at least two anchoring points and the expansion chamber having at least one fluid inlet. The expansion chamber capable of acquiring a minimum volume and a maximum volume. The flexible actuator is adapted to produce a traction force at the at least two anchoring points when the expansion chamber is inflated by pressurized fluid entering through the at least one fluid inlet.

[0015] Other objects and features of the invention will become apparent by reference to the following description and the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] A detailed description of preferred embodiments of the present invention is provided herein below, by way of example only, with reference to the accompanying drawings, in which:

[0017] Figures 1 a) and 1 b) are front elevational views of a flexible actuator in a relaxed state and in a contracted state according to a first embodiment of the invention;

[0018]FIGS. 2a) to e) are front elevational views of the flexible actuator of FIG. 1 through its various states from a relaxed state a) to a fully contracted state e) and intermediate states b) c) and d);

[0019]FIG. 3 is a front elevational view of a preferred embodiment of the flexible actuator of FIG. 1 shown with its elastomeric component removed to revealed its reinforcing filament component;

[0020]FIG. 4 is an enlarged exploded view of the weaving pattern of the various layers of the filament components of the preferred embodiment shown in FIG. 3;

[0021]FIG. 5 is front elevational view one embodiment of a fastening means for connecting an end of the flexible actuator to a structure or an object;

[0022]FIG. 6 is a schematic view of a simplified hydraulic or pneumatic circuit including a flexible actuator having a fluid inlet and a fluid outlet;

[0023]FIG. 7a) and 7 b) are front elevational views of a flexible actuator having multiple expansion chambers in series configuration;

[0024]FIG. 8 is a front elevational view of a flexible actuator having multiple expansion chambers in series-parallel configuration;

[0025]FIG. 9 is a front elevational view of a flexible actuator with multiple expansion chambers having multiple anchoring points; and

[0026]FIG. 10 is a front elevational view of a flexible actuator having multiple anchoring points.

[0027] In the drawings, preferred embodiments of the invention are illustrated by way of examples. It is to be expressly understood that the description and drawings are only for the purpose of illustration and are an aid for understanding. They are not intended to be a definition of the limits of the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0028] Figures 1 a) and 1 b) illustrate a flexible actuator 20 in a first relaxed state and in a second fully contracted state respectively. Flexible actuator 20 is made of an hermetic elastomeric material capable of expanding and stretching when submitted to a force. Flexible actuator 20 comprises at least one expansion chamber 22 defined by the inner wall of an expandable girdle 21 surrounding expansion chamber 22, at least two anchoring points 24 and 26 and flexible length sections 28, 29 of fixed diameter and various lengths connecting anchoring points 24, 26 to expansion chamber 22. Expansion chamber 22 comprises at least one fluid inlet to allow fluid under pressure to inflate expansion chamber 22 from the relaxed state depicted in FIG. 1a) to the contracted state depicted in Figure 1b). In the embodiment of Figures 1 a) and 1 b), flexible length section 28 comprises an internal conduit opening into expansion chamber 22 and anchoring point 24 comprises a fastening means 30 for securely connecting flexible actuator 20 to a structure 34 and to a fluid supply 33. Fastening means 30 is obviously provided with an internal fluid conduit such that expansion chamber 22 is in fluid communication with the fluid supply. Preferably, the internal diameter of expansion chamber 22 in the relaxed state (FIG. 1a) is marginally bigger than the internal diameter of the internal conduit of length section 28.

[0029] Flexible length section 29 connects one extremity of expansion chamber 22 to a symbolic mass M through second anchoring point 26. Anchoring point 26 comprises a second fastening means 32 for securely connecting flexible actuator 20 to mass M. Second anchoring point 26 is generally opposite the first anchoring point 24 and together define a working axis W-W along which a tension or traction force will be generated. The anchoring points 24 and 26 could have a wide variety of fastening means depending mainly on what the attachment is designed for. It must be noted that flexible actuator 20 is shown here in its simplest form having only a fluid inlet and no fluid outlet. It is understood however a fluid outlet is contemplated for fastening means 32 such that a complete hydraulic or pneumatic circuit may be designed around flexible actuator 20 (see FIG. 6). Therefore, in this simplified embodiment, fastening means 32 does not require an internal conduit for the pressurized fluid as it is not necessary in this case. Furthermore, length section 29 also does not require an internal conduit for the pressurized fluid.

[0030] As depicted in FIG. 1a), in the relaxed state, expansion chamber 22 is deflated and has a minimum volume. Expansion chamber 22 has an initial length x and an initial diameter y. Flexible actuator 20 is under an initial tension caused by the weight of mass M attached to anchoring point 26 and being pulled by the gravitational force. In use, pressurized fluid is supplied to expansion chamber 22 through the internal conduit of fastening means 30 and flexible section 28; the pressurized fluid inflates expansion chamber 22 by applying a pressure P onto the wall of expansion chamber 22. Expansion chamber 22 reaches a maximum volume as depicted in FIG. 1b). The diameter of expansion chamber 22 increases from x to x′ and the length of expansion chamber 22 is shortened from y to y′ thereby moving mass M by a distance D. Flexible actuator 20 is fully contracted when its expansion chamber 22 reaches its maximum volume as depicted in FIG. 1b). The fluid pressure applied to the inner wall of expansion chamber 22 is transformed into a traction force F on mass M along a working axis W-W by the shortening of expansion chamber 22 when the latter is being inflated and filled with pressurized fluid. The traction force developed by expansion chamber 22 is transmitted at both anchoring points 24 and 26 and translates into work depicted here by lifting mass M by a distance D. The speed of mass M is proportional to the inflow of pressurized fluid. To return flexible actuator to its initial relaxed state, the fluid under pressure is allowed to exit expansion chamber 22 through the internal conduit of fastening means 30 and flexible section 28 thereby deflating expansion chamber 22 and returning mass M to its initial position by decreasing the diameter of expansion chamber 22 from x′ to x and increasing the length of expansion chamber 22 from y′ to y.

[0031] In order to perform the described Work, the elastic properties of expandable girdle 21 must be different in the longitudinal working axis W-W defined by anchoring points 24 and 26 than its elastic properties perpendicular to longitudinal working axis W-W. More specifically, the elastic properties of the wall of expansion chamber 22 along longitudinal axis W-W must be such as to allow minimum stretching while its elastic properties perpendicular to longitudinal axis W-W must be such as to allow maximum stretching of expandable girdle 21. The difference in rate of expansion according to the orientation creates a tension force along the direction of the least rate of expansion, which in this case is along longitudinal working axis W-W. Without this difference of expansion rate, expandable chamber 22 would simply expand equally in all direction performing no Work on mass M. Furthermore, length sections 28 and 29 are made such that they do not inflate or expand at all and serve only as fluid conduit and anchoring means.

[0032] The fluid pressure P necessary to produce a traction force F capable of lifting a mass M consists of an initial pressure P1 to inflate expansion chamber 22 and stretch expandable girdle 21, and a pressure P2 proportional to the weight of mass M. The fluid pressure P equal to P1+P2 must first overcome the resistance to elongation of expandable girdle 21 which will occur in the direction having the weakest elastic properties such as perpendicular to axis W-W. The inner wall of expandable girdle 21 first stretching perpendicular to axis W-W, inflating expansion chamber 22 and applying a traction force F to mass M.

[0033]FIGS. 2a) through e) illustrate flexible actuator 20 through its various states from a relaxed state 2 a) to a fully contracted state 2 e) and intermediate states 2 b) 2 c) and 2 d). Anchoring point 24 of flexible actuator 20 is securely attached to a structure 37 and is connected to a pressure source such as a pump (not shown) by a typical three-way valve (not shown) allowing pressurized fluid in and out of expansion chamber 22. In FIG. 2a) flexible actuator 20 is in a relaxed state, expansion chamber 22 is at its minimum volume with only nominal pressure against its inner wall and flexible actuator 20 is under the initial tension of the weight of mass M.

[0034] In FIG. 2a), flexible actuator is in a relaxed state having an initial length L. Pressurized fluid is introduced into flexible actuator 20 and once the fluid pressure reaches the necessary pressure P, expansion chamber 22 begins to expand or inflate as illustrated in FIG. 2b), As the diameter x of expansion chamber 22 increases, the overall length L of flexible actuator 20 decreases at a proportional rate and lifts mass M. When mass M begins to move, flexible actuator is contracting and applying a traction force F to mass M. A steady inflow of pressurized fluid gradually increases the diameter of expansion chamber 22 through the intermediate stages 2 b, 2 c and 2 d. The wall of expandable girdle 21 stretching more rapidly perpendicular to longitudinal axis W-W thereby expanding the diameter of expansion chamber 22 more than along longitudinal axis W-W and applying a traction force on mass M. As previously mentioned, The speed of mass M is proportional to the flow of pressurized fluid; the higher the fluid debit, the faster flexible actuator 20 will inflate and move mass M. In FIG. 2e), expansion chamber 22 has reached its maximum volume and flexible actuator 20 is fully contracted.

[0035] The rate of change between diameter X and length L is dictated by the geometry of flexible actuator 20 and by the elastic properties of expandable girdle 21 specifically along the direction W-W at each location along the periphery of expansion chamber 22.

[0036] It must be noted that flexible actuator 20 only produces a traction force and is not capable of producing a compression force. Its flexibility prevents it from being able to produce a compression force at its anchoring points. Flexible actuator 20 is capable of pulling a mass M but cannot push a mass M since it is flexible. It must also be no

[0037]FIGS. 3a and 3 b illustrates a preferred embodiment of flexible actuator 20. Flexible actuator 20 is shown here without its hermetic elastomer component revealing its reinforced filaments enabling expandable girdle to display elastic behaviors that are different along longitudinal axis W-W than perpendicular to it. The elastomer component is a matrix reinforced with a series of oriented filament. The oriented filaments being stronger than the elastomer matrix, the weaving pattern of the filaments affect the elastic properties of expandable girdle 21. The elastomer matrix is however essential for sealing the fluid inside the flexible actuator 20.

[0038] As best shown in FIG. 3b, the weaving pattern of the filaments consists essentially of three types of oriented filaments. These are the longitudinal filaments 50, the angular filaments 52 and the circumferential filaments 54. Longitudinal filaments 50 are disposed all around the circumference of flexible actuator 20 and extend the entire length of flexible actuator 20 along the longitudinal axis W-W. Angular filaments 52 are woven in a criss-cross pattern around the circumference of flexible actuator 20 and also extend the length of flexible actuator 20. Circumferential filaments 54 are wounded almost perpendicular to longitudinal axis W-W and are concentrated along length sections 28 and 29 and around the transitional zones 56 and 56 linking length sections 28 and 29 to expansion chamber 22.

[0039] Longitudinal filaments 50 being in the longitudinal axis W-W are submitted to the bulk of the tension exerted by mass M and the bulk of the traction force produced by flexible actuator 20 when it is contracting. Longitudinal filaments 50 are securely woven or otherwise secured to each fastening means 30 and 32 such that efficient transfer of force occurs between longitudinal filaments 50 and anchoring points 24 and 26. When expansion chamber 22 is inflated by pressurized fluid, longitudinal filaments 50 are pushed perpendicular to the longitudinal axis W-W and this translates into a reduction of the length L of flexible actuator and a traction force being produced at each anchoring points 24 and 26. The traction force developed by expansion chamber 22 is transmitted mainly through longitudinal filaments 50 to both fastening means 30 and 32 and is further translated into Work when mass M is lifted by a distance D.

[0040] Angular filaments 52 are also woven together along the length of flexible actuator 20 and are submitted to a lesser amount the tension exerted by mass M and of the traction force produced by flexible actuator 20. However, the weaving pattern of angular filaments 52 dictates the general shape of expansion chamber 22 when the latter is inflated. Angular filaments 52 also reinforce length sections 28 and 29 and prevent the latter from expanding when pressurized fluid is introduced into flexible actuator 20. The weaving pattern changes at transitional zones 56 and 58 from a tighter pattern around length sections 28 and 29 to a looser pattern around expansion chamber 22. Angular filaments 52 are also securely woven or otherwise secured to each fastening means 30 and 32 such that efficient transfer of force occurs between angular filaments 52 and anchoring points 24 and 26.

[0041] Circumferential filaments 54 are woven tightly around length sections 28 and 29 and less tightly around transitional zones 56 and 58. Their main purpose being to prevent circumferential expansion of length sections 28 and 29 and rigidly control the circumferential expansion of transitional zones 56 and 58 when fluid pressure is exerted onto the inside walls of flexible actuator 20. Circumferential filaments 54 are also woven tightly around fastening means 30 and 32 to secure longitudinal and angular filaments 50 and 52 and the elastomer matrix to fastening means 30 and 32.

[0042] The braiding or weaving pattern of longitudinal, angular and circumferential filaments 50, 52 and 54 of flexible actuator 20 as shown in FIG. 4, is exploded to illustrate one possible weaving pattern of the various filaments. The braiding pattern is shown when the expansion chamber is expanded. Longitudinal filaments 50 are interwoven here with angular filaments 52. Although not essential, this pattern helps maintain longitudinal filaments spread evenly around the circumference of expansion chamber 22. As can be seen, circumferential filaments 54 are wounded around the interwoven filaments 50 and 52 in the transitional zone 54 and along length section 28.

[0043] Flexible actuator 20 may comprise a plurality of layers of longitudinal, angular and circumferential filaments 50, 52 and 54. Preferably, a first layer of longitudinal filaments 50 is positioned over a first layer of woven angular filaments 52 such that during the expansion of expansion chamber 22, angular filaments 14 evenly push longitudinal filaments 50 outwardly under the fluid pressure. A second layer of angular filaments 14 should also be placed over the first layer of longitudinal filaments 50 in order to insure that longitudinal filaments 50 will conform to the contours of expansion chamber 22. Various patterns of weaving longitudinal filaments 50 into angular filaments 52 are possible as long as a sufficient amount of angular filaments 52 is placed inside longitudinal filaments 50 to provide sufficient strength to push longitudinal filaments 50 outwardly and efficiently transfer the fluid pressure P on the wall of expansion chamber 22 to longitudinal filaments 50. The down side of not providing a first layer of angular woven filaments 52 placed in front of a layer of longitudinal filaments 50 is that longitudinal filaments 50 could only count on the adhesive property between itself and the chosen elastomer matrix that seals and harness the fluid pressure inside. Under a traction force, longitudinal filaments 50 are forced inwardly and without a first layer of woven angular filaments 52, the fluid pressure would tend to push in between each longitudinal filaments 50, at the weakest points, and the elastomer matrix could very well rip delaminate and separate from longitudinal filaments 50 disabling efficient transfer of fluid pressure inside expansion chamber 22 into a traction force. At this time, the adhesion of an elastomer to a filament of any kind is not strong enough to ensure the best possible transfer of the pressure force to the longitudinal filaments 50. However, a particular blend of elastomer and adhesive could, in theory, be capable of a sufficiently strong mechanical link to transfer the pressure force to longitudinal filaments 50.

[0044] As previously mentioned, it is preferable to also have a layer of angular filaments 52 above longitudinal filaments 50 in order to conformed longitudinal filaments 50 to the contours of expansion chamber 22 but also to ensure that in the transitional zones 56 and 58, the optimal curvature of longitudinal filaments 50 is maintained thereby minimizing the risk of damage to them during expansion.

[0045]FIG. 5 a cross sectional view illustrating one embodiment of a fastening means which is connected to the ends of length sections 28 and 29. The fastening means is a cylindrical fastener 60 comprising a threaded portion 62 and a conical anchoring portion 64. Anchoring portion 64 comprises an array of rigid hooks 66 disposed along the length and around the circumference of conical anchoring portion 64. An internal conduit 68 extends through threaded portion 62 and anchoring portion 64 to allow fluid to flow therethrough. Each longitudinal filaments 50 and is woven or attached to at least one rigid hook 66 and is therefore securely connected to fastener 60. Preferably, each longitudinal filament 50 is wounded around conical anchoring portion 64 and is anchored to a plurality of rigid hooks 66. By winding each longitudinal filament 50 so that it is anchored to a plurality of rigid hooks 66, the shearing forces on longitudinal filaments 50 at each rigid hooks is spread over the circumference of conical anchoring portion 64. Ideally, each longitudinal filament 50 is wounded more than once around conical anchoring portion 64 such that an optimum attachment is obtained. Anchoring portion 64 is conical so that the various layers of filaments may be wounded one on top of the other starting from the smaller end 70 to the larger end 72 of anchoring portion 64. Angular filaments 52 may also be anchored to rigid hooks 66 in a similar fashion. Finally, circumferential filaments 54 are wounded over the various layers of longitudinal and angular filaments 50 and 52. As previously stated, various weaving patterns are contemplated for the main body of flexible actuator 20 and this applies also to the weaving of the various filaments around conical anchoring portion 64.

[0046]FIG. 5 also shows cylindrical fastener 60 threaded into a threaded aperture 74 of structure 34. A typical hydraulic or pneumatic hose 76 has a threaded end connected to the opposite side for supplying fluid under pressure to the flexible actuator 20 connected thereto.

[0047] Flexible actuator 20 is preferably made by weaving the angular and longitudinal filaments 50 and 52 together in the shape of the expansion chamber 22 fully expanded i.e. in the fully contracted position. The fully contracted state of flexible actuator 20 is the most critical state for longitudinal and angular filaments 50 and 52. In this stretched position, the gaps between each longitudinal filament 50 and between each angular filament 52 are the widest and the elastomer matrix is thinnest. Furthermore, it subjects longitudinal filaments 50 to the sharpest bends especially around transitional zones 56 and 58. The filament winding should therefore be done on a shape having the contours of flexible actuator 20 fully contracted, to precisely control precisely the potential gaps between each filament 50 and 52 in the contracted state and to control the maximum radius of bending of longitudinal filaments 50. The evenness of the weaving pattern of both longitudinal filaments 50 and angular filaments 52 must be precise enough to minimize any irregularities in the weaving which could result in creating weak points due to larger spaces between each filaments. In the transitional zones 56 and 58, angular filaments 52 must be carefully woven to support and maintain longitudinal filaments 50 such that undue bending will not occur when flexible actuator is fully contracted.

[0048] Fabricating flexible actuator 20 in its contracted state enables a better control of the position of each filament 50 and 52 in that state. It also allows the control of the thickness of the elastomer matrix in this critical state which again will ensure that no weak spots are created by a thinner membrane of elastomer and provide an even thickness of the expandable girdle 21 when expansion chamber 22 is inflated.

[0049] The weaving can be done with any suitable filament winding machine either with or without a mold. The weaving pattern should follow the general guide lines of a first and last layer of angular filaments sandwiching the longitudinal filaments. There can be more than one layer of longitudinal filaments 50 to add strength to the actuator as long as longitudinal filaments 50 are properly enveloped and supported inside and outside expansion chamber 22 by a layer of angular filaments 52 to transfer the fluid pressure force to longitudinal filaments 50. Flexible actuator 20 is essentially fabricated like a hydraulic hose with various layers of woven fiber reinforcement blended into an elastomer matrix. Flexible actuator 20 is fabricated in alternative layers of elastomer and woven filaments. A first layer of elastomer is form in the shape of the actuator in its fully contracted state and a first layer of angular filaments 52 is woven over or into the first layer of elastomer. A second layer of elastomer is applied to the form and a second layer of longitudinal filaments 50 alone or a blend of longitudinal and angular filaments 50 and 52 is then woven onto or into the second layer of elastomer. A third layer of elastomer is applied and a third layer of angular filaments 52 is woven into the third layer of elastomer. If the second layer is a blend of longitudinal filaments 50 and angular filaments 52, many layers of this type may be added without sandwiching them between two layers of angular filaments 52. A plurality of layers are fabricated in this fashion; each layer of longitudinal filaments 50 adding to the overall strength of flexible actuator 20. A final layer is applied and woven in the same fashion as the first one consisting essentially of angular filaments 52 for the purpose of maintaining longitudinal filaments 50 conform to the contours of the fully expanded expansion chamber 22. Two or more first and last layers of woven angular filaments 52 may be necessary when high pressures and high forces are required.

[0050] The flexible actuator can also be fabricated by adding the elastomer once the skeleton of woven filaments is complete. It can also be fabricated in variations of two or three layers of woven filaments in between layers of elastomer. Many variations of weaving patterns are possible and various manufacturing methods are available without departing from the spirit and scope of the present invention.

[0051] The flexible actuator fabricated in the fully contracted state is therefore in its stable condition in this state and will maintain this shape until a traction force is applied to its extremities. The elastomer matrix so constructed will tend to return to the fully contracted state and provide an initial tension to flexible actuator when it is stretched into the fully extended position or relaxed state as depicted in FIG. 1a). This initial tension of flexible actuator 20 is produced by the elastomer matrix and adds to the overall force flexible actuator 20 can produce. Furthermore, It lowers the minimum pressure necessary inside the expansion chamber to produce work by initiating a movement in the longitudinal axis W-W.

[0052]FIG. 6 illustrates a basic workable hydraulic or pneumatic circuit which includes a flexible actuator 20. The basic circuit comprises a motor 80 driving a pump 81 which supplies pressurized fluid to a two-way valve 82 feeding a hose 83 provided with a no return valve 84. Hose 83 is connected to a fluid inlet 85 of flexible actuator 20, flexible actuator having a fluid outlet 86 connected to a pressure valve 87. When two-way valve 82 is closed, pressurized fluid from pump 81 is fed into flexible actuator 20 which contracts to perform a task. Pressure valve 87 preventing an excess of pressure into flexible actuator 20. Pressure valve 87 is controlled such that when flexible actuator 20 must return to its initial relaxed state, pressure valve 87 is open to allow pressurized fluid to exit flexible actuator 20 through fluid outlet 86. Other components such as debit valves to control the rate of contraction of flexible actuator 20 may added to the circuit depending on what is required of the system.

[0053]FIGS. 7a and 7 b illustrate further embodiments of flexible actuators. Flexible actuators 100 and 105 respectively are shown, each having multiple expansion chambers 22 arranged in series. The construction is similar to flexible actuator 20 wherein longitudinal filaments 50 extend the entire length of flexible actuators 100 and 105 and angular filaments 52 are also woven around the entire length of each flexible actuators 100 and 105. In a similar fashion as previously described, longitudinal filaments 50 transform the pressure forces inside each expansion chamber 22 into a traction force at each anchoring points 24 and 26. The mid-sections 102 in between each expansion chamber 22 are woven like length sections 28 and 29 with circumferential filaments 54 such that no expansion will occur between the multiple expansion chambers 22. This configuration has the advantage of producing a longer displacement since for each expansion chamber 22, the length of flexible actuator is reduced by a given amount so that having two or more expansion chambers 22 increases the overall displacement of flexible actuators 100 and 105. The displacement of each expansion chamber 22 being added to the next expansion chamber 22. In these particular embodiments, for a identical expansion chamber, flexible actuator 100 will move mass M twice the distance of flexible actuator 20 and flexible actuator 105 will move mass M three time the distance of flexible actuator 20. However, with expansion chambers 22 in a series configuration, the addition of expansion chambers does not increase the overall strength of the flexible actuators.

[0054]FIG. 8 shows a flexible actuator 125 having multiple expansion chambers 22 in series-parallel configuration. In this embodiment, flexible actuator 125 comprises three rows of expansion chambers 22 in series: A central row 126 comprising three expansion chambers 22 and two lateral rows 126 and 127 each comprising two expansion chambers 22. The rows of expansion chambers in series are constructed in a similar fashion as flexible actuators 100 and 105 with mid section 102 separating each expansion chamber 22. Again, longitudinal filaments 50 extend the entire length of a row of expansion chambers 22 and angular filaments 52 are also woven around the entire length of each row 126, 127 and 128. As in the previous embodiments, longitudinal filaments 50 transform the pressure forces inside expansion chambers 22 into a traction force at each anchoring points 130 and 132. The length sections 136, 137 and 138 of each row 126, 127 and 128 are attached to a single fastening means and each row is supplied with pressurized fluid through their respective length sections 136, 137 and 138. Length sections 136, 137 and 138 are braided together with circumferntial filaments 54 to secure each to anchoring point 130. Similarly, length sections 146, 147 and 148 of each row 126, 127 and 128 are attached to a single fastening means at anchoring point 132.

[0055] In this series-parallel configuration, the overall strength of flexible actuator 125 is increased by the number of rows of expansion chambers 22. The flexibility of each row of expansion chambers 22 allows them to conform to each other and expand in harmony. Ideally, expansion chambers 22 of adjacent rows are shifted and positioned near the mid sections of the adjacent rows to provide room for expansion. Adjacent rows are combined to have their expansion chambers 22 aligned with mid section or the length sections of their neighbor so as to minimize the total space occupied by flexible actuator 125 when they are fully contracted.

[0056] This embodiment is one of a multitude of arrangements possible with a series-parallel configuration. There could be more or less rows, expansion chambers of various sizes to accommodate adjacent rows and so on.

[0057]FIG. 9 illustrates another embodiment of a flexible actuator 150 having multiple expansion chambers 22. Three rows of expansion chambers 22 are connected together at one extremity but separated at their other extremities. Three fluid lines 152 supply each row 153, 154 and 155 with pressurized fluid. Pressurized fluid may be supplied to only one row. For example, if pressurized fluid is fed to row 154 only, a traction force will be generated along the longitudinal axis Z-Z only, pulling mass M in along that axis. If pressurized fluid is fed to all three rows 153, 154 and 155, a traction force will be generated along the longitudinal axis Y-Y pulling mass M in along that axis. Length sections 162, 164 and 166 are braided together with circumferential filaments 54. In this embodiment, flexible actuator 150 is provided with a fluid outlet 158 which enables pressurized fluid to exit and complete a normal hydraulic or pneumatic circuit as shown in FIG. 6.

[0058]FIG. 10 illustrates a variant of the connection of a flexible actuator 175 to a structure 180. Pressurized fluid is fed to expansion chamber 22 through a central inlet line 176 but is anchored to structure 180 by two flexible length sections 177 and 178. Length sections 177 and 178 do not have an internal conduit and only serve to anchor flexible actuator 175 to a structure and transfer the traction force generated by expansion chamber 22. Obviously, longitudinal filaments 50 extend around length sections 177 and 178 in order to transfer the traction force to structure 180. A single length section 179 is here connected to a mass M. Longitudinal filaments 50 therefore extend the entire length of flexible actuator 175 from anchoring point 182, along length section 179, around expansion chamber 22 and along each length section 177 and 178.

[0059] As can be seen in FIGS. 7, 8, 9 and 10, various combination of flexible actuators are possible. Single expansion chambers may be placed side by side in parallel or in series to suit mechanical requirement. Various connections are also possible. Because of their inherent elastic behavior, flexible actuators can apply forces in a wide array of curves. If two actuators are placed side by side, their straight line longitudinal axis will blend together because the outer surface of the expansion chambers is flexible and will conform to its neighboring expansion chamber and to its surroundings. The flexibility of the flexible actuator enables to let two actuators interfere with each other and therefore work more closely together. The flexibility of the actuator simplifies greatly the positioning of an array of actuators in a confined area. It also makes it much easier to double or triple the overall force by putting actuators side by side and anchoring them at common anchoring points.

[0060] The above description of preferred embodiments should not be interpreted in a limiting manner since other variations, modifications and refinements are possible within the spirit and scope of the present invention. The scope of the invention is defined in the appended claims and their equivalents. 

The embodiments of the invention for which an exclusive privilege or property is claimed are defined as follows:
 1. A flexible actuator comprising: an expansion chamber defined by an inner wall of an expandable girdle, said expandable girdle connected to at least two anchoring points; said expansion chamber having at least one fluid inlet; said expansion chamber capable of acquiring a minimum volume and a maximum volume; said flexible actuator adapted to produce a traction force at said at least two anchoring points when said expansion chamber is inflated by pressurized fluid entering through said at least one fluid inlet.
 2. A flexible actuator as defined in claim 1 wherein said flexible actuator generate work when said expansion chamber expands between said minimum dimension and said maximum dimension.
 3. A flexible actuator as defined in claims 1 or 2 wherein said flexible actuator acquires a relax state when said expansion chamber is at said minimum dimension, a fully contracted state when said expansion chamber is at said maximum dimension, and a partially contracted state when said expansion chamber is in between said minimum dimension and said maximum dimension.
 4. A flexible actuator as defined in claims 1 to 3 wherein said expandable girdle comprises an elastomeric matrix reinforced with filaments.
 5. A flexible actuator as defined in claim 4 wherein said fibers include a plurality of filaments oriented randomly.
 6. A flexible actuator as defined in claim 4 wherein said fibers include a plurality of filaments braided in a crisscross pattern.
 7. A flexible actuator as defined in claim 6 wherein said fibers include a plurality of filaments oriented along a longitudinal direction generally corresponding to an axis defined said at least two anchoring points.
 8. A flexible actuator as defined in claim 7 wherein said filaments oriented along a longitudinal direction extend continuous along said expansion chamber.
 9. A flexible actuator as defined in claim 8 comprising at least one layer of said filaments braided in a criss-cross pattern and at least one layer of said filaments oriented along a longitudinal direction.
 10. A flexible actuator as defined in claim 9 comprising a plurality of layers of said filaments braided in a criss-cross pattern and a plurality of said filaments oriented along a longitudinal direction.
 11. A flexible actuator as defined in claim 10 wherein said expansion chamber comprises a fluid outlet separate from said fluid inlet, said pressurized fluid entering through said fluid inlet and exiting through said fluid outlet.
 12. A flexible actuator as defined in claim 1 wherein said at least two anchoring points comprise fastening means for connecting said flexible actuator to a structure.
 13. A flexible actuator as defined in claim 12, wherein said fluid inlet coincides with one of said fastening means.
 14. A flexible actuator as defined in claim 13, wherein said fluid outlet coincides with another of said fastening means.
 15. A flexible actuator as defined in claim 14, wherein said structure comprises a fluid conduit in fluid communication with said fluid inlet for supplying said expansion chamber with pressurized fluid.
 16. A flexible actuator as defined in claim 1 wherein said expandable girdle is an elastomeric body; said inner wall of said expandable girdle having varying thickness distributed around said expansion chamber.
 17. A flexible actuator comprising: an expansion chamber defined by an inner wall of an expandable girdle, said expandable girdle connected to at least two anchoring points; said expansion chamber having at least one fluid inlet; said expansion chamber capable of acquiring a minimum volume and a maximum volume; said flexible actuator adapted to transform a fluid pressure force against said inner wall of said expandable girdle into a traction force at said at least two anchoring points when said expansion chamber is inflated by pressurized fluid entering through said at least one fluid inlet. 